Field
Exemplary embodiments relate to a liquid crystal display.
Discussion of the Background
Flat panel display devices which are presently known include a liquid crystal display (LCD), a plasma display panel (PDP), an organic light emitting display (OLED) device, a field effect display (FED), an electrophoretic display device, and the like.
Particularly, the liquid crystal display is one of flat panel display devices which are currently most widely used, and includes two substrates of display panel in which field generating electrodes such as a pixel electrode and a common electrode are formed, and a liquid crystal layer interposed therebetween.
The liquid crystal display displays an image by applying a voltage to the field generating electrodes to generate an electric field in the liquid crystal layer, thereby determining an orientation of liquid crystal molecules of the liquid crystal layer based on the generated electric field and controlling polarization of incident light.
The liquid crystal display has an active matrix structure formed of data lines and gate lines that correspond to a resolution. A data signal and a gate signal are output in time for a light emission period during which pixels emit light, and the data signal is output and the gate signal is not output for a blank period during which pixels do not emit light, so it does not apply a load to the pixels corresponding to the data signal during the blank period. The data lines are directly connected with a driver IC on a lower substrate of display panel and transmit the data signals, and a common voltage Vcom can be applied to an upper substrate of display panel through an OP AMP.
In the blank period, the driver IC outputs black data signal but does not output the gate signal so that capacitors of the pixels cannot be charged, that is, a load free state occurs. When entering the light emission period, the gate signal is output and accordingly the data signal is output so that a transient load is generated. In this case, an output voltage of a DC/DC converter is dropped due to an unexpected current. When a power voltage AVDD derived from the output voltage of the DC/DC converter and a first gamma voltage Vgamma1 are reversed, an internal circuit of the driver IC is damaged, and accordingly, the power voltage AVDD and the first gamma voltage Vgamma1 should have a predetermined difference. That is, the first gamma voltage is lower than the power voltage AVDD, and accordingly luminance is decreased.
In addition, a transient current should be supplied corresponding to the transient load according to the entering of the light emission period in the DC/DC converter that supplies a current. Although capacity of the AMP should be increased according to performance of the transient load, it is difficult to manufacture an AMP having tolerance to a peak current stress.
Meanwhile, since the electrostatic discharge (ESD) applied to the upper substrate of display panel and thus flows into the liquid crystal display does not include an additional discharging path, electric shock is given to the OP AMP through the common electrode and the electric shock is also applied to the driver IC through data lines from the common electrode.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.